// 2^63 + 2^62 + ... + 2^1 + 2^0
	// which means we have to flip all bits to 1 in an uint64
	var total uint64
	return ^total

	// 2^63 + 2^62 + ... + 2^1 + 2^0 == 2^64 - 1
	return 1<<64 - 1

	var tmp uint64
	return ^tmp >> (64 - n), nil

	return 1<<n - 1, nil